A pioneering blood test correctly identified cancer in almost two thirds of cases it highlighted so could lead to earlier diagnosis, a study has found.
The Galleri test, which screens for more than 50 cancers and is being trialled in the NHS, searches for the “fingerprint” of dozens of deadly cancers and can even identify signs before symptoms show.
It identifies DNA shed by cancer cells in the bloodstream, giving the earliest signs a patient may have the disease.
More than 23,000 people without symptoms from the US and Canada were analysed and assessed for at least a year as part of the Pathfinder 2 trial.
Results showed that of those found to have a “cancer signal” detected in their blood, 61.6% went on to be diagnosed with the disease.
Galleri, developed by US biotechnology firm Grail, is also highly accurate in identifying when the disease is not present, the study found – correctly ruling it out in almost all (99.6%) cases.
For those with cancer, it identified which organ or tissue was affected with a 92% success rate, meaning time and money could be saved on further scans and other tests.
The Pathfinder 2 study looked at how the Galleri test may be used in a real-world setting, alongside regular screening programmes for difference cancers such as breast and bowel.
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An NHS Galleri trial on how well the test works in screening people without symptoms is expected to be published next year.
Sir Harpal Kumar, Grail’s president of international business and biopharma, said the trial results showed Galleri detected “seven times as many cancers as the other screening programmes put together”, meaning it will help in “transforming cancer outcomes”.
Modelling suggests the Galleri test could be effective as an annual blood test in people from the age of 50, when cancer cases begin to rapidly increase, he said.
Earlier this year, research published in the journal BMJ Open found that an annual blood test for cancer could lead to 49% fewer late-stage diagnoses and 21% fewer deaths within five years.
Professor Nitzan Rosenfeld, director of the Barts Cancer Institute in London, said the Galleri test results were “impressive”.
However, other experts have reacted more cautiously.
Professor Clare Turnbull, from the Institute of Cancer Research, called for further research into whether such tests reduced cancer death rates.
And Anna Schuh, professor of molecular diagnostics at the University of Oxford, warned that the test gets it wrong when it calls a positive result “almost half of the time”, which she said was “disappointing as it is only fractionally better compared to tossing a coin”.
